Idiotypes are serological markers of antibody variable (V) regions which allow the study of the antibody repertoire and also can be used for clonally specific manipulation of immunity. In ongoing projects, we are studying antibody responses to Ia.7, with the goal of understanding diversity and V region expression in this response. In addition, we are studying induction of anti-Ia.7 antibody responses by anti-idiotype in vivo, as a model for anti-idiotype vaccination. Specific projects: 1) A study of antibody diversity is continuing involving sequencing of heavy and light chain variable regions of anti-Ia.7 hybridomas, in collaboration with the lab of Dr. Tom Wood, FCRF. Techniques have been worked out for avoiding cloning of an aberrant MRNA present in SP2/0 cells. A few complete sequences have now been obtained, and variable regions for a few additional chains have been or are in the process of being cloned. 2) Using a panel of monoclonal anti-idiotopes, we had demonstrated that potency of an anti-idiotope for inducing antigen-specific immunity is not predicted by any single immunochemical parameter, thus ruling out several models. IL-2 given in vivo along with anti-idiotype had little effect on the response to a poor inducer, making a difference in idiotype-specific helper T cells unlikely. Idiotope mapping of the induced populations revealed a surprising diversity of combining sites related to same idiotypic family and able to bind Ia.7, yet structurally distinct. Inducing potency thus is probably related to degree of representation in the B cell repertoire. 3) We are applying a new method of idiotype-carrier conjugation. Antibodies are biotinylated on carbohydrate sites of the constant region.